Marble Cake

Preparation

1. Preheat oven to 350 degrees. Grease 2 cake pans and line them with parchment paper. I used an 8 inch circular pan. You could do 3 pans if you have enough batter and want to do a 3 layer cake. 
2. Make the vanilla cake batter. In a large bowl, combine the butter and sugar. Add in the eggs. Add flour, baking powder, and salt. Add milk and pure vanilla extract. Mix well. 
3. Make the chocolate cake batter. In another large bowl, mix together the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt. Add the butter and then the oil. Add the pure vanilla extract, milk, and eggs, and mix well. 
4. Add even spoonfuls of vanilla cake batter and chocolate cake batter alternatively to both cake pans. The batter should be about 1 inch deep. 
5. Using a butterknife, swirl the cake batter to make a marbled pattern. The knife should lightly touch the bottom of the pan so that the swirl goes deep and isn't just surface level. 
6. Bake the cakes in the oven for about 30 minutes or until a toothpick comes out clean. If you do 3 cake layers, then the cooking time will be more like 22 minutes. 
7. If you have leftover batter, you can make some cupcakes to eat separately or to place on top of the marble cake. Bake the cupcakes for 18-20 minutes. 
8. Once the cakes are out of the oven, use a butter knife around the edges of the cake pans to separate the cake from the pan. Let the cakes cool for about 10 minutes. I like to carefully flip the cake pans onto a cutting board or wire rack. The parchment paper is key in being able to flip the cakes over successfully. 
9. In a medium-sized bowl, combine the powdered sugar and cocoa powder to make the chocolate frosting. Add in butter, and then vanilla extract and milk. Mix together with a spatula and then use an egg beater or mixer machine if you have one. This makes the frosting smoother and creamy. If the batter is too thick, you can add a splash of milk at a time. If you want more frosting, you can double the amounts for the frosting recipe. I ended up doubling the frosting recipe for this cake. 
10. Once the cakes have completely cooled, frost them. Completely cover the cakes and their sides in chocolate buttercream frosting. Place one cake layer, rounded side down, on a serving plate and then generously frost the cake layer. Add next cake layer and frost it. You can decorate the cake with M&M's, sprinkles, piped frosting, or just let it be like I did!